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N7XXMA Working To Restore Nature ' Addendum One to Remedial Action Plan March 1, 1993 Coca-Cola Former Distribution Facility, Stockton, California 54006.01 four other borings. Soil type was primarily clayey and sandy silt. Cumulative results of laboratory analyses of sort samples are summarized in Tables A-1 and A-2, and are listed 1 under October/November 1990 data TPHg was nondetectable in all eleven borings, with the exception of B-15/VEW-2 and B-16/VEW-3. TPHg in these two borings ranged from nondetectable to 630 ppm (at 5 feet in B-16/VEW-3). TPHd was nondetectable in all borings except B-14/VEW-1 through B-17/VEW-4, and ranged from nondetectable to 50 ppm (in B-16/VEW-3 at 15 feet). BTEX was nondetectable in five of the borings, and in the other six borings ranged from nondetectable to 44 ppm total xylenes (in B-16/VEW-3) ' TPHg soil concentration contours at depths of 0 to 30 feet are shown graphically in Plate 4. PNAs were nondetectable in all of the 14 samples tested, with the exception of B- 16/VEW-3 which contained 3,500 ppm naphthalene at a depth of 5 feet, as reported in Table A-2 ' In November 1990, the groundwater sample from newly constructed well MW-6 indicated nondetectable concentrations of TPHg, and BTEX. TPHd was detected at a concentration of 64 ppb Preliminary_Vapor Extraction Test ' In November 1990, a preliminary vapor extraction test was conducted to determine the feasibility of using vapor extraction as a soil remediation alternative (USTEC, September 1991). The test was conducted on VEW-1 through VEW-4 and MW-1, MW-4, and MW-5 ' Applied wellhead vacuums ranged from about 50 to 66 inches of water. Induced vacuums in the observation wells were measured, and ranged from 0.1 to about 6 inches of water Distances between wells ranged from 12.5 to 94 5 feet. Extracted soil vapor concentrations ' were not determined, nor was the effective radius of influence. One year later in November 1991,four additional vapor extraction wells (VEW-5 through VEW-8)were installed. These four new wells were not previously tested for a soil vapor extraction system. Boring logs for 1 these four wells were included in the fourth quarter 1991 momtormg report (USTEC, 1992), but results of soil laboratory analyses for these vapor wells were not available to RESNA at this writing. uarterly Groundwater Monitoring, Quarterly groundwater monitoring was initiated after the wells were installed. Table A-4 summarizes depth to water (DTW) measurements and groundwater elevations. DTW ranges from about 67 feet to about 71 feet, and groundwater elevation is about 52 feet below mean sea level (MSL). The groundwater flow direction is generally toward the northeast, at a shallow gradient of about 0.002 feet per foot. ' A-4